The closures, and now Khamenei's decision, have exposed the reformists' weakness despite a strong electoral mandate. The courts and many other levers of power remain firmly in the hands of conservatives opposed to Mr. Khatami's social and political reforms.

Yesterday, deputies had scheduled a parliamentary debate and a vote to ease a Draconian press law. Passage was virtually assured.

But the intervention of Khamenei, who has final say in key matters of state, forced a suspension of the matter among shouted protests and even scuffles on the floor of the chamber.

"If the enemies infiltrate our press, this will be a big danger to the country's security and the people's religious beliefs. I do not deem it right to keep silent," the leader said in a letter to parliament. "The present press law has succeeded to a point to prevent this big plague. The [proposed] bill is not legitimate and in the interests of the system and the revolution."

Speaker Mehdi Karroubi, a veteran revolutionary cleric, said deputies had no choice but to submit to Khamenei's will.

"Our Constitution has the elements of the absolute rule of the supreme clerical leader and you all know this and approve of this. We are all duty-bound to abide by it," the speaker said.

The decision to kill the bill provoked a storm of criticism on the floor, forcing the speaker to turn off the microphones and to issue repeated demands for order. Stung by the leader's move, some pro-reform deputies were weighing possible resignation, while their leaders met behind closed doors to consider a letter of protest to Khamenei.